Grey Box Modeling of Gas Temperature for a High-Speed and High-Temperature Heat-Airflow Test System

Round 1

Reviewer 1 Report

1. The content of the Manuscript

 The study presents a non-stationary lumped model for gas temperature control in HHHTS (The high-speed high-temperature heat-airflow test system). The research results are highly specialized and cannot be used for other purposes.

 

The gray box modeling used is also known as semi-physical simulation. Model based on both insight into the system and experimental data is constructed.  Model based on HHHTS heat balance.  The unknown free parameters of the model are estimated using system identification. To identify  the temperature T and the delay coefficient a, a recursive least squares algorithm with an auxiliary variable and the cross-correlation function method are used.

The authors claim that the gray box model is new. But in Russia, such an approach has been known since the 60s of the last century and was developed by the school of Viktor Kafarov, Alexander Zackheim and others.

Simulation and experimental results show that  the mathematical model  has high accuracy and can be used for the control of gas temperature.

 2.   Rating the Manuscript

 

 The question is original and well defined. The results do not provide progress in modern knowledge, as they contain the solution of a standard modeling problem.

 

The data and analyses presented appropriately. The results are interpreted appropriately, but are not significant. All conclusions are substantiated and confirmed by the results. Hypotheses and speculations are identified carefully.

The study correctly designed and technically sound. Methods described with sufficient. There is no data in the article that would allow another researcher to reproduce the results.

The conclusions are not of interest to the readers of the journal. The paper will be of interest only to a limited circle of people. The benefit of the publication of this work will probably be after the revision of the article.

3. Recommended Revisions.

а) The article should be supplemented with an analysis of the differences between the obtained results and other works. What new or unused methods did the authors use? Why couldn't results be obtained using CFD programs?

б) How can the results be used for other equipment?

Author Response

Q1.  The article should be supplemented with an analysis of the differences between the obtained results and other works. What new or unused methods did the authors use? Why couldn't results be obtained using CFD programs?

Our response: Thank you for your comment. The differences between this paper and other works are shown in the following aspects. First, the object of this paper is HHHTS, which is a high-speed hot wind tunnel and belongs to the combustion field; at present, no one has used gray box modeling to model its gas temperature. Second, although the grey box modeling method adopted in this paper has been applied in many fields, it seems not new, but the difference between this paper and other work is that different methods are used to identify different types of parameters, and a new grey box modeling model is proposed, that is, after completing the first principle modeling, according to the characteristics of the parameters to be identified, The recursive least squares method with auxiliary variables and correlation analysis method are used to identify uncertain parameters and time delay respectively. Finally, in the field of high-speed combustion, CFD is generally used to establish the distributed parameter model of gas temperature in the combustor. This paper attempts to establish the Lumped parameter model of gas temperature, and studies the problem from different angles, which is also the reason why the results of this paper are not obtained by CFD. In a word, this paper is different from other works in terms of research objects, research questions and research methods, and has certain innovation and value. We have added the above content to the article, and highlighted it in yellow. You can easily find it in the revised version (5.3. Analysis of the differences).

Q2.  How can the results be used for other equipment?

Our response: Thank you for your comment. Although the method proposed in this paper is aimed at modeling the gas temperature of HHHTS, it is a general modeling method, which can be easily used for modeling other complex objects with similar characteristics (parameter time-varying, time delay). The basic method is as follows: first, the first principle modeling is applied to establish a preliminary model of the object, and then the input and output data are obtained through experiments on the research object; finally, the recursive least square method with auxiliary variables is used to identify the uncertain parameters of the object, and the time delay of the object is obtained by using the correlation analysis method, so as to finally establish the mathematical model of the object. In the conclusion, we have added the extended application of the research method in this paper, and highlighted it in yellow. You can easily find it in the revised version.

Author Response File: Author Response.doc

Reviewer 2 Report

The authors proposed new method to obtain the temperature of the gas temperature for a high-speed and high-temperature heat-airflow test system using Grey-box model.

The experimental measurement data is used to validate the accuracy of the proposed prediction.

This paper is recommended to be accepted.

Comments:

(1) The authors should provide the limitations of the studied temperature and Mach number for high temperature and high speed.

(2) The authors should add the measurement equipment error of the test system in this paper.

 

Author Response

Q1. The authors should provide the limitations of the studied temperature and Mach number for high temperature and high speed.

Our response: Thank you for your comment. In section 5.1, when we introduced the experimental equipment, we introduced three types of HHHTS. Their Mach number ranges from 0.2 to 1.5 and their temperature ranges from 400 ℃ to 1700 ℃. The above is the applicable temperature and speed range of this method. We emphasized this in the revised version. We highlighted it in yellow, and you can easily find it in the revised version.

Q2. The authors should add the measurement equipment error of the test system in this paper.

Our response: Thank you for your comment. In this paper, the sensor we use to measure temperature is K-type thermocouple. In order to reduce measurement error, we choose K-type thermocouple that meets the national I accuracy standard, and its error is ± 0.4%.We have given this error in the revised version. We highlighted it in yellow, and you can easily find it in the revised version.

Author Response File: Author Response.doc